A fleet of miniature helicopter drones mounted with thermal imaging cameras are to be deployed to combat graffiti-spraying gangs on the German railway network.

The drones, which fly at an altitude of 450-ft, will be used at graffiti “hot spots” such as the big German cities of Berlin, Leipzig, Cologne and Hamburg, a spokesman for Deutsche Bahn confirmed.

The use of drones against vandals is the latest indication of the growing civilian market for unmanned aerial reconnaissance. More than 400 drone systems were being developed by firms based in Europe, according to an EU report last September.

The drones cost $80,000 each and are manufactured by the German firm Microdrones, which also markets the machines for landscape photography, analysing traffic accidents and monitoring crops. They will be painted in Deutsche Bahn’s red livery.

Jens-Oliver Voss, a spokesman for Deutsche Bahn, said privacy laws meant that drones would not be used near stations, where members of the public might be filmed.

“They will be used in combination with security guards, identifying graffiti-sprayers so they can be apprehended by security forces, who can hand them over to police,” he said.

Deutsche Bahn, which spends euros 7.6-million a year removing graffiti, is refusing to say how many drones it has bought.